In an imaging device such as a camera, a digital camera, a camcorder, and binoculars, a captured image may be disturbed by user's hand shaking. For such an imaging device, there has been developed an image stabilization function which reduces an adverse effect of user's hand shaking on an imaging function. A method for realizing the image stabilization function encompasses a module shift method, a lens shift method, a sensor shift method, and the like. Among these, the lens shift method corrects an optical axis of an optical system, by (i) incorporating a correction lens having a vibration gyro mechanism and the like into an imaging device and (ii) moving the correction lens in a direction that allows a vibration due to user's hand shaking to be canceled. This method makes it possible to control fluctuations of light that reaches a light receiving surface (e.g., a film or an image sensor). This consequently makes it possible to reduce the adverse effect of user's hand shaking on the imaging function. The lens shift method is superior to the module shift method and the like in terms of smaller size and smaller thickness.
However, the lens shift method has a problem in that in some cases, an initial position of the correction lens to be used for an optical axis correction does not coincide with a center of a correction mechanism in which the correction lens is stored. Such non-coincidence between the initial position of the correction lens and the center of the correction mechanism occurs due to, for example, (a) variations of spring constants or the like of members supporting the correction lens, (b) a mounting error which occurs during incorporation of the correction lens and the like into the imaging device, (c) external force which acts on the imaging device in which the correction lens and the like are incorporated, (d) an aging deterioration, and so forth.
FIG. 7 is a view illustrating a state in which an initial position of a correction lens 1011 does not coincide with a center of a correction mechanism (space S) in which the correction lens 1011 is stored, and is also a view illustrating a calibration device 1000 and a calibration method according to a conventional technique. As illustrated in FIG. 7, the calibration device 1000 includes the correction lens 1011 and a drive device 1013 which moves the correction lens 1011. Note that the calibration device 1000 may use, as the drive device 1013, a drive device of another device (e.g., an imaging device) used together with the calibration device. The correction lens 1011 is stored in the space S between a left end 19a and a right end 19b. The correction lens 1011 moves within a movable range R which is horizontally symmetrical with respect to a center p, so as to cancel a vibration due to hand shaking. The center p is an initial position of a center of the correction lens 1011. As described above, the center p (initial position) of the movable range R of the correction lens 1011 does not coincide with a center c of the space S (correction mechanism) in which the correction lens 1011 is stored. In this case, the drive device 1013 does not move the correction lens 1011 away from the center p beyond a boundary position q which is a position horizontally symmetrical to a right end position b with respect to the center p. That is, the non-coincidence between the initial position (center p) of the correction lens 1011 and a center (center c) of the correction mechanism in which the correction lens 1011 is stored produces an unusable region Q (a region between a left end position a and the boundary position q) to which the drive device 1013 does not move the correction lens 11. Further, the drive device 1013 cannot move the correction lens 1011 with an output beyond a rated output of the drive device 1013. Accordingly, in practice a range within which the drive device 1013 can move the correction lens 1011 may be limited to a rated output range Ri (a range between a left rated output position α and a right rated output position β) narrower than the movable range R.
In order to reduce such an unusable region Q, Patent Literature 1 discloses an image stabilization device which allows a camera itself to automatically adjust an adjustment value to be used for calculating a correction lens position from outputs of respective correction lens position detection circuits at both ends of a movable range of a correction lens. FIG. 8 is a view illustrating a calibration device 2000 and a calibration method according to a conventional technique disclosed in Patent Literature 1. The calibration device 2000 is similar in configuration to the calibration device 1000 illustrated in FIG. 7. However, the calibration device 2000 is different from the calibration device 1000 in that the calibration device 2000 includes a drive device 2013 which has a rated output range Ri containing a space S as illustrated in FIG. 8. Provided with the drive device 2013, the calibration device 2000 moves the correction lens from a left end position a to a right end position b and thereby carries out calibration so that a center p coincides with a center c. Note that, in FIG. 8, a center p after calibration is indicated as “pa” and a movable range R after calibration is indicated as “Ra”. That is, Patent Literature 1 discloses a method for calibrating an initial position of the correction lens 1011 by (i) causing the drive device 2013 to move the correction lens 1011 from a left end 19a to a right end 19b and (ii) detecting positions of the correction lens 1011 during the movement of the correction lens 1011 so as to detect left and right end positions (the left end position a and the right end position b) of the space S in which the correction lens 1011 is stored.